Numerous devices have been developed to adjust tension along chain flights between sprockets. Most tensioning devices are mounted to support frames and include pivoted or otherwise movable chain engaging guides for engaging the chain flights and urging them together. Such apparatus, because of the requirement for a frame or other mounting device, is not universally adaptable to all chain drive systems. One example of such a device is illustrated in U.S. Pat. No. 1,401,169 to McCuen which discloses a pivoted belt tightener. The tightener is mounted by a swing arm to a frame that is stationary relative to the moving belting flight. U.S. Pat. No. 3,295,383 to Allen discloses a drive belt tightening idler. The tightening idler is mounted by a swing arm to a frame and is urged by a spring mechanism against one of the belt flights.
U.S. Pat. No. 2,963,918 to Blakstad discloses a chain or belt tensioning device. The device must be mounted to a frame separate from the chains for selective operation. Similar apparatus is shown in U.S. Pat. No. 976,115 to Bard and U.S. Pat. No. 2,210,276 to Brimer.
All the above apparatus function adequately in special applications in which framework is available to mount the tensioning device.
U.S. Pat. Nos. 1,338,405 to Stickney; 4,068,535 to Sheets; 3,941,006 to Brodesser; and 3,926,063 to Mayfield all disclose self supporting belt or chain tighteners that include rollers for engaging opposed flights of belts or chains and are adjustable toward or away from one another against opposed flights of the belts or chains. With rollers, expense is incurred in manufacturing and maintaining the roller bearings that are involved.
U.S. Pat. Nos. 4,662,862 and 4,798,562 to Matson both disclose chain tighteners with fixed friction blocks that engage the side plates of opposed chain flights. The chain side plates slide over the blocks. With such guides, excessive wear is either experienced along the guides or the roller chain side plates where they rub against the guide surfaces.
A primary object of the present invention is to provide a novel solution to the problem of tensioning roller chains by providing a roller chain tensioner with opposed roller guide surfaces that include roller engaging surfaces thereon for contacting the chain rollers, and grooves alongside the roller engaging surfaces that loosely receive the chain side plates. When engaged, the chain rollers will roll across the present roller guide surfaces and the chain side plates will move loosely through the guide grooves.
A further object is to provide such a tensioning device that is adapted to fit chains of varying size.
A still further object is to provide such a tensioning device with a simplified means by which the tensioning device may be mounted to a chain and adjusted to selectively vary tension along the flights of the chain.
These and still further objects and advantages will become apparent upon reading the following detailed description which, taken with the accompanying drawings, disclose a preferred form of the present invention.